The present invention relates to a safety device which can be activated, in particular, by a moving body such as a person or an object, intended in particular to form a safety gate.
In cable installations for transporting people, in particular skiers, safety devices must be provided in order, in the majority of cases, to shut down installation. Such devices are commonly called safety gates, end-of-piste gates, anti-twisting gates or non-alighting gates. Indeed, it is particularly desirable to detect the passage of a user in a place where he should not normally be, to detect on a chairlift a passenger who has not left his chair on the arrival area or a safety bar/footrest unit which has not been raised prior to getting on, or to detect on a ski tow a user who has not released his equipment at the end of the arrival platform, or the extendable part of towing equipment which has not resumed its upper position after having been released by a user on the arrival platform.
Various devices have already been proposed in order to overcome these safety problems.
A safety device is known, in particular, which comprises a post anchored vertically in the ground and on which is mounted a rigid rotary bar which activates an electric switch controlling the shutdown of the installation when it is stressed in rotation. However, this known safety device has disadvantages. These are that if the action exerted on the bar has a direction different from that capable of causing it to rotate, the electric switch will not be activated and the bar consequently forms an obstacle for the skier. Depending on the thickness of the snow, the position of the bar must be adjusted frequently so as to maintain a given height between this bar and the upper surface of the snow. Since the post is anchored in the ground, it must be of sufficient height and resist the pressure resulting from the sliding of the snow blanket on the slope. The post constitutes a danger for the skier who runs the risk of impaling himself on it. Furthermore, the permanent presence of the post complicates the work of making the arrival areas, in particular in the event of a large snowfall or when using mechanized machines.
Another known safety device consists of a wire held taut between two supports. This wire may consist of an electrical conductor capable of being pulled out when the user passes through it, or alternatively of a cord connected to the control member of an electric switch, as described in the Patent FR-A-2,163,987. The main disadvantage of this known safety device lies in the fact that the wire can become wound around the skier or around the towing equipment and is thus likely to hold him or it back dangerously, the shutting down of the installation never being instantaneous.
The object of the present invention is to overcome the disadvantages of the known safety devices and it provides a safety device permitting, in particular, the prevention of any injury to people or any damage to the machinery which could be caused by the safety device itself, whatever the circumstances.
The safety device of the invention can advantageously be used in the field of installations for transporting skiers but can, of course, be used in any fields where the passage of people or objects is to be detected.